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| United States Patent |
5,552,476
|
|
Halling
|
September 3, 1996
|
Hydrolyzed silane emulsions and their use as surface coatings
Abstract
Novel and highly reactive hydrolyzed silane emulsions are achieved by
emulsifying a hydrolyzable alkoxysilane (e.g., or the like) in water in
the presence of an effective amount of an emulsifier of sufficiently high
HLB value (preferably 14 or greater) to simultaneously retain said
hydrolyzable alkoxysilane compound in a substantially totally hydrolyzed
state and inhibit said resulting hydrolyzed alkoxysilane compound from
self-condensation. Such reactive emulsions containing hydrocarbon silanes
are useful to produce durable coatings that impart water repellency and
lubricity to substrates having siliceous, cellulosic or proteinaceous
surfaces.
| Inventors:
|
Halling; Robert A. (Wilmington, DE)
|
| Assignee:
|
E. I. Du Pont de Nemours and Company (Wilmington, DE)
|
| Appl. No.:
|
248613 |
| Filed:
|
May 12, 1994 |
| Current U.S. Class: |
524/837; 106/287.12; 427/387; 524/858 |
| Intern'l Class: |
C08J 003/03; C08J 003/07; B05D 001/00; B01F 017/54 |
| Field of Search: |
524/837,858
106/287.12
427/387
|
References Cited
U.S. Patent Documents
| 2476307 | Jul., 1949 | Klein et al. | 260/448.
|
| 3012006 | Dec., 1961 | Holbrook et al. | 260/46.
|
| 3422131 | Jan., 1969 | Pittman et al. | 260/448.
|
| 3442664 | May., 1969 | Heine | 106/2.
|
| 3450738 | Jun., 1969 | Blochl | 260/448.
|
| 4024306 | May., 1977 | Takamizawa et al. | 427/387.
|
| 4089882 | May., 1978 | Takamizawa et al. | 260/448.
|
| 4342796 | Aug., 1982 | Brown et al. | 427/136.
|
| 4478911 | Oct., 1984 | Price | 428/332.
|
| 4525213 | Jun., 1985 | Linn | 106/2.
|
| 4525425 | Jun., 1985 | Church | 428/428.
|
| 4549003 | Oct., 1985 | Lim et al. | 528/42.
|
| 4648904 | Mar., 1987 | DePasquale et al. | 106/2.
|
| 4687707 | Aug., 1987 | Matsuo et al. | 428/336.
|
| 4689181 | Aug., 1987 | Blatch | 260/408.
|
| 4865910 | Sep., 1989 | Inoguchi et al. | 428/268.
|
| 4874431 | Oct., 1989 | Fey et al. | 106/2.
|
| 4877654 | Oct., 1989 | Wilson | 427/387.
|
| 4889747 | Dec., 1989 | Wilson | 427/221.
|
| 4983459 | Jan., 1991 | Franz et al. | 428/410.
|
| 4990377 | Feb., 1991 | Wilson | 427/387.
|
| 5011963 | Apr., 1991 | Ogawa et al. | 556/485.
|
| 5051129 | Sep., 1991 | Cuthbert et al. | 106/2.
|
| 5059649 | Oct., 1991 | Maxson et al. | 524/398.
|
| 5124467 | Jun., 1992 | Rodgers et al. | 556/427.
|
| 5274159 | Dec., 1993 | Pellerite et al. | 556/485.
|
Other References
Tailoring Surfaces With Silanes, Chemtech Dec. 1977, pp. 766-778.
Alastair W. Stupart, Water Repellent Treatments For Brickwork, Oct. 1993
pp. 809-811.
|
Primary Examiner: Glass; Margaret
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of U.S. Ser. No. 08/206,779
filed Mar. 4, 1994, herein incorporated by reference.
Claims
I claim:
1. A reactive aqueous emulsion comprising: (a) an alkoxysilane compound
emulsified in water, wherein said alkoxysilane compound is represented by
the formula:
##STR6##
where: R is a hydrocarbon radical of 8 to 24 carbons; R' are the same or
different alkyl radicals of 1 to 3 carbon atoms; and n=2 to 10 and (b) an
effective amount of an emulsifier of sufficiently high HLB value to
simultaneously retain said alkoxysilane compound in a hydrolyzed state and
inhibit the resulting hydrolyzed alkoxysilane compound from
self-condensation.
2. A reactive aqueous emulsion of claim 1 wherein R is a hydrocarbon
radical with 16 or greater carbons.
3. A reactive aqueous emulsion of claim 1 wherein said hydrolyzed
alkoxysilane compound is octyltris(2-(2-methoxyethoxy)ethoxy)silane.
4. A reactive aqueous emulsion of claim 1 wherein said hydrolyzed
alkoxysilane compound is
dodecyltris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)silane.
5. A reactive aqueous emulsion of claim 1 wherein said hydrolyzed
alkoxysilane compound is
octadecyltris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)silane.
6. A process for coating a substrate comprising the steps of:
(a) emulsifying in water (i) an alkoxysilane compound represented by the
formula:
##STR7##
where: R is a hydrocarbon radical of 8 to 24 carbons; R' are the same or
different alkyl radicals of 1 to 3 carbon atoms; and n=2 to 10 and (ii) an
effective mount of an emulsifier of sufficiently high HLB value to
simultaneously retain said alkoxysilane compound in a hydrolyzed state and
inhibit the resulting hydrolyzed alkoxysilane compound from
self-condensation thus forming a reactive aqueous emulsion; and
(b) contacting a substrate with said reactive aqueous emulsion of step (a).
7. A process for coating a substrate according to claim 6 wherein R is a
hydrocarbon radical with 16 or greater carbons.
8. A process for coating a substrate according to claim 6 wherein said
hydrolyzed alkoxysilane compound is
octyltris(2-(2-methoxyethoxy)ethoxy)silane.
9. A process for coating a substrate according to claim 6 wherein said
hydrolyzed alkoxysilane compound is
dodecyltris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)silane.
10. A process for coating a substrate according to claim 6 wherein said
hydrolyzable alkoxysilane compound is
octadecyltris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)silane.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to stable aqueous emulsions of hydrolyzed
silanes and their application to various substrates to impart water
repellency and lubricity. More specifically but not by way of limitation,
the present invention relates to aqueous emulsions of a silane and an
effective amount of an emulsifier having a hydrophile-lipophile balance,
HLB, sufficiently high to retain the silane in a stable aqueous emulsion
in substantially a hydrolyzed state.
2. Description of the Related Art
It is known that hydrolyzable silanes can be applied to surfaces to impart
hydrophobic or water repellency properties (see, B. Arkles, Chemtech,
1977, 766). These silanes are applied to the surfaces either dissolved in
a volatile organic solvent or as aqueous solutions or emulsions. With the
solvent based products, the solvent must be evaporated once the solution
is applied to the surface. In addition, the hydrolyzable silane must be
contacted with water or sufficient adsorbed moisture on the surface being
treated to hydrolyze the silane so that it may chemically bond to the
surface to form a durable coating (see for example, U.S. Pat. Nos.
4,342,796 and 4,525,213). The presence of volatile solvents in coating
formulations is generally harmful to the environment and may be hazardous
due to their flammability. In addition, treatments of surfaces with these
hydrolyzable silanes frequently require the use of elevated temperatures
and certain catalysts to accelerate the hydrolysis of the silane and the
condensation with the surface to achieve the desirable effects (see for
example, U.S. Pat. Nos. 4,478,911 and 4,874,431).
When the hydrolyzable silanes are applied from the more preferred aqueous
solutions or emulsions, buffers must be added to the aqueous mixtures to
maintain the pH of the mixture within narrow limits to prevent premature
hydrolysis of the silane and subsequent self-condensation to a polymeric
polysiloxane (see for example, U.S. Pat. Nos. 4,889,747 and 4,990,377).
Such a polymeric structure is no longer dispersible in the aqueous medium,
and contains a reduced number of active sites that can bond the silane to
the substrate. Generally acidic or basic conditions will accelerate this
hydrolysis. However, if the aqueous emulsion is stabilized with a buffer
to prevent hydrolysis on storage, this buffer must be overcome once the
silane is applied to the substrate to now permit the hydrolysis to take
place, and bonding with the substrate to occur. The prior art therefore
teaches that for the preferred aqueous systems, the silane must be
retained in the emulsions in a non-hydrolyzed state to achieve adequate
storage stability, and that hydrolysis must then be caused to take place
when the silane is applied to the substrate so that the proper bonding can
occur between the silane composition and the surface to produce the
desirable properties.
SUMMARY OF THE INVENTION
In view of the above and unlike the solvent based hydrolyzable silanes and
the buffer-stabilized aqueous trialkoxsilane emulsions of the prior art it
has now been discovered that the aqueous silane emulsions of this
invention contain the silane in an essentially completely hydrolyzed state
and thus ready for instant bonding to the substrate to provide repellency
and lubricity properties. Notwithstanding this apparent total hydrolysis
and thus highly reactive state of the silane, the unique aqueous emulsions
of the instant invention do not permit the hydrolyzed silanes to
self-condense to high molecular weight, water insoluble, polysiloxane
structures while in this emulsified state. Thus these emulsions are
generally stable to long periods of storage of one year or more, are
stable to broad ranges of pH, typically from a pH of 2.0 or less to about
11.0, are stable to temperatures of 80.degree. C. or greater, and
frequently are stable to repeated freezing and thawing conditions without
undergoing coagulation and precipitation of the silane.
In the broadest sense of the above observed high reactivity of the
emulsion, wherein apparently total hydrolysis of the silane compound in
the micelle is achieved simultaneously with long term inhibition of the
self-condensation reaction, is felt to be characteristic of the use of any
readily emulsifiable alkoxysilane in combination with an effective amount
of an emulsifier of very high HLB value. Thus, the present invention
provides for novel aqueous emulsions of unique reactivity and stability
comprising: (a) an alkoxysilane compound emulsifiable in water; and (b) an
effective amount of an emulsifier of sufficiently high HLB value to
simultaneously retain the alkoxysilane compound in a hydrolyzed state and
inhibit the hydrolyzed alkoxysilane compound from self-condensation.
In one specific embodiment of this invention and consistent with the
acknowledged prior art recognition that durability is associated with the
presence of multiple hydrolyzable groups leading to cross-linked siloxane
structures upon condensation with a substrate, the present invention
further provides for a trialkoxysilane of the following formula be
employed:
##STR1##
Wherein: R is a hydrocarbon radical of 8 to 24 carbons; R' are the same or
different alkyl radicals of 1 to 3 carbon atoms; and n=2 to 10.
The improved method of using the emulsion for surface coating of a
substrate according to the instant invention comprises the steps of:
(a) emulsifying in water (i) an alkoxysilane represented by the formula:
##STR2##
where R is a hydrocarbon radical of 8 to 24 carbons; R' are the same or
different alkyl radicals of 1 to 3 carbon atoms; and n=2 to 10 and (ii) an
effective amount of an emulsifier of sufficiently high HLB value to
simultaneously retain said alkoxysilane compound in a hydrolyzed state and
inhibit said hydrolyzed alkoxysilane compound from self-condensation thus
forming a reactive aqueous emulsion; and
(b) contacting a substrate with said reactive aqueous emulsion of step (a).
One object of this invention is to produce aqueous emulsions of selected
hydrolyzable silanes and/or hydrolyzable alkoxy substituted silanes that
exhibit good stability on storage under a broad range of pH conditions.
Another object is to provide such aqueous emulsions wherein the
hydrolyzable silane is retained in a highly reactive state by virtue of
essentially total hydrolysis of the alkoxy moiety and, simultaneously,
self-condensation is inhibited. Still another object of this invention is
to provide an improved process that takes advantage of the highly reactive
state of the silane in the emulsion to render substrates water repellent
and to impart a high lubricity surface that significantly reduces the
tendency to scratch by the application of the aqueous emulsions of the
hydrolyzed silanes without the need for special curing operations.
DESCRIPTION Of THE PREFERRED EMBODIMENTS
In describing and exemplifying the various features and aspects of the
present invention and in explaining how the present invention differs from
and is distinguishable over the previously known compositions and methods
of use along with their corresponding advantages, it should be appreciated
that the novelty of the present invention should be viewed as being the
composite of achieving a highly reactive yet stable aqueous emulsion
capable of producing a durable, chemically bonded coating as opposed to
the specific properties resulting from the simple coating of the
substrate. Even though a specifically preferred embodiment of this
invention relates to stable aqueous emulsions of hydrolyzable reactive
silanes that are storage stable and that react with the substrate surfaces
to impart water repellency and lubricity, in a broader sense the invention
relates generically to any desirable property associated with the silane
coating. As such, the following description will utilize the preferred
silanes that encompass essentially all of these features with the
understanding that certain features of the invention have much broader
implications and as such the specific embodiment should not be interpreted
as being unduly limiting.
Aqueous emulsions of formula (1), in addition to imparting water repellency
to surfaces coated therewith, also impart improved lubricity. Generally,
desired lubricity is observed for compounds wherein R contains at least 8
carbon atoms and is particularly true of those compounds wherein R
contains 16 or more carbon atoms. This increased lubricity is of course
more readily observed if the substrate coated has a smooth surface. This
increased lubricity, that is, decreased coefficient of friction, renders
the surface much more scratch resistant, a particularly important benefit
for glass and tile surfaces.
The silanes useful in this invention are represented by the following
formula:
##STR3##
wherein: R is a hydrocarbon radical of 8 to 24 carbons; R' are the same or
different alkyl radicals of 1 to 3 carbon atoms; and n=2 to 10. The
preferred compositions are R=one or more hydrocarbon radicals of 16 to 24
carbon atoms; R'=methyl; and n=2 to 10. Especially preferred, because of
low cost of the starting materials and high efficiency in imparting
desirable scratch resistance to treated surfaces is R=C.sub.18 hydrocarbon
radical; R'=methyl; and n=2or3.
The silanes of this invention are prepared by methods known in the art (see
Kirk-Othmer, Encyclopedia of Chemical Technology, Third Edition, Vol. 20,
and R. C. Mehrota, Pure And Applied Chem., 13, 111, 1966). The preferred
method is by reacting the corresponding trichlorosilane with the proper
ether alcohol, such as diethylene glycol monomethyl ether or triethylene
glycol monomethyl ether, for example, according to the following equation:
##STR4##
An alternate method also useful for the preparation of the preferred
silanes for this invention involves the transesterification of the
corresponding alkyltrimethoxy or alkyltriethoxy silanes with the ether
alcohol, with removal of the methanol or ethanol byproduct. This reaction
usually requires an acid or base catalyst, such as p-toluenesulfonic acid
or sodium methoxide, to accelerate the reaction.
Any solvent inert to the reactants and products may be used in the reaction
to provide the hydrocarbonsilane ether alkoxides of this invention. If the
reactants and products are liquid and mutually miscible under the reaction
conditions, the solvent may be omitted. Solvents such as hexane, heptane,
toluene and cyclohexane are suitable.
The temperatures suitable for these reactions are those that will effect
completion within a reasonable length of time. Temperatures ranging from
about 0.degree. C. to 160.degree. C., or to the boiling point of the
solvent, may be used. Usually temperatures of from about 25.degree. C. to
about 120.degree. C. are employed. Reaction times from about 2 hours up to
24 hours are usually adequate to complete the reaction.
The hydrolyzable silanes of the compositions described above possess unique
properties that enable them to be formulated into the stable but reactive
aqueous emulsions that impart water repellency and lubricity to surfaces
to which they are applied without the use of organic solvents, which
increase costs and may degrade the environment.
The silanes suitable for preparation of these aqueous emulsions must
possess hydrolyzable groups that impart sufficient hydrophilicity to the
silane to permit the initial emulsifiability in the aqueous medium, with
or without the emulsifier. In the case of the preferred compositions
described above, wherein R=C.sub.18 alkyl and R'=methyl or ethyl, n must
equal 2 or greater to produce aqueous emulsions with the proper emulsifier
that exhibit long term stability. When n=0 or 1, a stable emulsion is not
formed but rather an insoluble polymeric precipitate is produced by
hydrolysis and condensation of the silane. For silanes with R=C.sub.8 to
C.sub.18 hydrocarbon groups, stable emulsions may be prepared with n=2 or
greater, however, for R=greater than C.sub.18, n must be 3 or greater to
achieve stable emulsions. Hydrolyzable groups other than those derived
from polyether alcohols may be used to impart sufficient hydrophilicity to
the silanes to permit stable aqueous emulsions to be formed. Hydrolyzable
groups derived from polyalcohols may be used, however, they are generally
more difficult or more costly to produce. The reaction of the polyalcohols
with an alkyltrichlorosilane or alkyltrimethoxysilane to form the
hydrolyzable silane structures frequently produces polymeric, crosslinked
structures that possess significantly reduced water miscibility.
Emulsifiers usable to prepare the stable aqueous emulsions of the
hydrolyzable silanes of this invention may be chosen from cationic,
anionic, and non-ionic types. The preferred emulsifiers are those that
have an HLB ("The HLB System" published by ICI America's Inc., Wilmington,
Del.) value greater than 16, and preferably greater than 18. Emulsifiers
with HLB values below 16 do not form stable aqueous emulsions with
compositions of this invention. Mixtures of emulsifiers that each meet the
above HLB requirements may be used, if they are compatible with one
another. Suitable emulsifiers include, but are not limited to, C.sub.8-18
alkyltrimethylammonium quaternary salts, alkali metal
alkylbenzene-sulfonates, linear alkyldiphenyletherdisulfonates,
alpha-olefin sulfonates, alkyl and alkylether sulfates, C.sub.12-18
alkyldimethylammonium salts, polyethoxylated C.sub.12-18 alkylammonium
salts and highly ethoxylated alkyl and arylalcohols. The type of
emulsifier used may influence the magnitude of the desirable properties
that are imparted to the substrates that are treated with the aqueous
emulsions. Generally cationic emulsifiers that meet the above HLB
requirements are preferred for preparing aqueous emulsions of the
hydrolyzable silanes of this invention that will impart superior lubricity
and scratch resistance properties to treated siliceous surfaces.
The aqueous emulsions of this invention are prepared by mixing the
emulsifier with water and then slowly adding the silane, employing
standard agitation techniques. After the materials are thoroughly blended,
the emulsions must stand for a period of a few hours to several days, with
or without further agitation, to permit the alkoxysilane to hydrolyze and
the emulsion to achieve the stable equilibrium composition. The emulsions
generally change from a clear colorless uniform mixture to a hazy or white
milky emulsion during this standing period. The addition of an acid, such
as a non-oxidizing organic acid like acetic acid, and/or the use of mild
heating will accelerate the change to the stable equilibrium composition.
Analysis of the unique aqueous emulsions of this invention by nuclear
magnetic resonance spectroscopy indicated that the alkoxysilanes have
undergone hydrolysis to produce hydroxysilanes which are believed to
possess the structure
##STR5##
and possibly low molecular weight oligomers thereof. However, unlike
trihydroxysilanes in water mixtures without the proper emulsifier, these
silanes do not undergo condensation to produce insoluble polymeric
structures, but remain in a stabilized, emulsified state in the aqueous
formulation. This hydrolysis in the aqueous emulsified state may require
from a few minutes, for emulsions where the pH has been lowered to a value
of 2 to 4 to hasten the reaction, to several days.
The stable aqueous emulsions may vary from a slightly hazy mixture to white
milky formulations. Particle size measurements by light scattering
techniques (Coulter N4MD instrument) have shown particle sizes of from
less than 10 nm to about 300 nm. Most frequently the particle sizes range
from less than 10 nm to about 100 nm, indicative of true microemulsions
rather than emulsions.
The concentration of the emulsifier in the preferred emulsions is critical
and varies with the particular emulsifiers and silanes. The optimum
concentration for any given emulsifier/silane system is readily determined
by routine procedures. In general, for the silanes of the present
invention, the emulsifier may be present at concentrations of from 5 to
100, or more, weight percent based on the weight of the silane. The
preferred concentrations of emulsifiers are in the range of about 10 to
50%. The concentration of the silane may be from 0.01 to 50% by weight,
based on the total emulsion, preferably from 0.01 to 25 weight percent for
practical reasons.
A uniform, hazy to milky appearance of an emulsion of this invention, with
no separation of solids, is indicative of its stability. Poor stability is
recognized by separation of the silane as a polymeric species due to
condensation to form less soluble siloxane structures and/or gel
formation. The preferred hydrocarbon silane emulsions of this invention
containing an emulsifier are stable for over 6 months when stored at
ambient temperatures. Many are stable at elevated temperatures of up to
60.degree. C. and higher for over two months. Many emulsions, particularly
when prepared at emulsifier levels of 30% or greater based on silane
weight, are stable to alternate freezing and thawing conditions.
Additionally, many of the emulsions are stable at pH levels as high as 11
or as low as 2, if the emulsifier is also unaffected by such conditions.
The emulsions of this invention may also be diluted to 0.01% or lower
without loss of stability.
The aqueous emulsified hydrocarbon silanes of this invention will interact
with functional groups on the surface of substrates to produce a durable
coating of the silane that imparts water repellency to those substrates.
The hydrocarbon silane repellent treating compositions are most useful for
imparting repellency and lubricity to substrates having siliceous,
cellulosic or proteinaceous surfaces, and to polymer substrates having
pendant active hydrogen groups, such as polyesters and polyamides. Typical
of treatable substrates are wood, brick, concrete, masonry, stone, glass,
ceramic tile, natural and synthetic fibers, fur, and leather.
In addition to this water repellency, hydrocarbon silane emulsions of this
invention also impart enhanced lubricity to treated, smooth surfaces. The
magnitude of this increased lubricity is generally proportional to the
length of the hydrocarbon group, R. This enhanced lubricity of smooth
surfaces that have been treated results in increased resistance of the
surface towards scratching. This is a particularly important benefit for
surfaces such as glass and ceramic tile.
The substrates are treated by coating the emulsions of this invention on
the substrate surface and allowing the coated surface to dry. No special
curing step is required to achieve the durable repellency and lubricity
properties, however, heat may be applied to accelerate the drying process.
The treated surface, after drying, may be washed with water to remove
residual emulsifier and thereby increase the water repellency. The
resultant product is a substrate having bonded thereto a surface layer of
the hydrolyzed/condensed form of the compound of formula (1) and/or (2).
Various additives such as pigments and antioxidants may also be
advantageously included in the emulsions of the present invention. It is
also contemplated that mixtures of more than one silane compound may be
used in the emulsions. In addition, it is also envisioned that the
emulsions of this invention may be combined with other aqueous
formulations to impart the unique properties of this invention to those
formulations.
The following examples are presented to more fully demonstrate and further
illustrate various individual aspects and features of the present
invention. In doing so, the preferred hydrocarbon trialkoxysilanes are
intentionally employed as being generally illustrative of the enhanced
reactivity of the hydrolyzed emulsion compositions and generally
illustrative of the resulting durable coatings of the process using these
hydrocarbon silanes while being specifically illustrative of imparting
useful and desirable repellency and or lubricity to substrate surfaces. As
such, the examples are felt to be non-limiting and are meant to illustrate
the invention, but are not meant to be unduly limiting in any way,
particularly with respect to ultimate properties and utility of the coated
surfaces.
EXAMPLE 1
Preparation of Octyltris(2-(2-methoxyethoxy)ethoxy)silane
To a dry flask fitted with an agitator, thermometer, additional funnel and
reflux condenser was charged 222.8 g (0.90 mole) of octyltrichlorosilane
and 225 g of heptane. The mixture was blanketed with nitrogen, heated to
80.degree. C. and 333.7 g (2.78 mole) of 2-(2-methoxyethoxy)ethanol was
added slowly over a 2 hour period. Hydrogen chloride was evolved from the
mixture. After the addition was complete heating of the reaction was
continued for 24 hours at 80.degree. C. Then the solvent and all volatile
components of the mixture were removed under vacuum, producing 451 g of
the clear, colorless liquid product.
EXAMPLE 2
Preparation of Dodecyltris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)silane
The procedure of Example 1 was repeated with 151.8 g (0.50 mole) of
dodecyltrichlorosilane and 200 g. of heptane. Under nitrogen 254.2 g (1.55
mole) of 2-(2-(2-methoxyethoxy)ethoxy)ethanol was added over 3 hours at
80.degree. C. followed by heating of the reaction for an additional 48
hours. Vacuum stripping of all volatiles left 350 g of the clear, pale
yellow liquid product.
EXAMPLE 3
Preparation of Octadecyltris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)silane
The procedure of Example 1 was repeated with 387.5 g (1.0 mole) of
octadecyltrichlorosilane and 800 mL of heptane. Under nitrogen 508.4 g
(3.10 mole) of 2-(2-(2-methoxyethoxy)ethoxy)ethanol was added at
80.degree. C. over 4 hours. After heating the reaction for an additional
48 hours and removal of all volatile components under vacuum, 780 g of the
pale yellow liquid product were obtained.
EXAMPLES 4-13
Aqueous Emulsions of Examples 1-3
The following aqueous emulsions of the silanes of Examples 1-3 were
prepared by adding the silane slowly to a well agitated mixture of the
emulsifier and acetic acid in water. The emulsions were agitated for 15
minutes after the addition of the silane, and the emulsions were allowed
to stand for at least 72 hours to permit complete hydrolysis of the silane
to occur and for the emulsion to achieve its equilibrium state. All
emulsions were made at a concentration of 10 wt. % of the starting silane.
______________________________________
Emulsifier Conc.
Acetic
Example
Silane Emulsifier
(% of silane Wt.)
Acid* pH
______________________________________
4 Ex. 1 A 40% 10% 2.6
5 1 B 30 5 3.5
6 1 C 40 10 3.5
7 1 D 40 15 3.5
8 2 A 40 5 2.6
9 2 B 30 5 3.5
0 2 C 40 10 3.5
11 2 D 40 15 3.0
12 3 A 40 10 2.4
13 3 B 30 5 3.5
14 3 D 40 15 3.5
______________________________________
*% based on weight of silane
Emulsifier
A = Hexadecyltrimethylammonium chloride
B = C.sub.14-16 Alpha Olefin Sulfonate, sodium salt
C = Octadecylamine60 E.O.
D = Octadecyldimethylammonium chloride
EXAMPLE 15
Lubricity of Treated Glass
The durable lubricity enhancing effects achieved by treating surfaces with
compositions of this invention were demonstrated by measuring the static
friction of glass slides that were treated with the aqueous emulsions of
examples 4-14. For each of the emulsions of examples 4-14, 50.times.75 mm
precleaned glass slides were treated by immersing them in the emulsion
containing 0.1 wt. % of the silane. The slides were wiped dry with a
lintless tissue and the static friction values measured. After the
measurements were made, the slides were rinsed thoroughly with deionized
water, dried and again the static friction values were determined.
The static friction values were determined by ASTM Method D 4518-91, Test
Method A, using an inclined plane. Two treated glass slides were placed
face to face on the level plane, a 500 g weight was placed on the slides
to produce a force of 125 g per square inch of surface, and the
inclination of the plane was increased at a rate of 14 degrees per minute.
The static friction value was determined as the tangent of the angle at
which the two slides just began to slide over each other. Triplicate
values were determined for each of three pairs of slides for each
treatment. The values shown in Table 1 show the excellent lubricating
properties imparted by treatment with compositions of this invention. They
also show a slight improvement in the lubricating values as the length of
the R group of equation 1 is increased, and the influence that the
emulsifier has on the lubricity properties achieved by the silane
emulsions.
Each of the treated glass slides was then rated for its relative resistance
to scratching by placing the slide on a weighing balance and using the
corner edge of a new glass slide to scratch over the surface with a total
force of 1000 g. The relative scratch resistance of the slides is also
listed in Table I. A value of 1 indicates the most difficult to scratch.
All treated slides were very difficult to scratch compared with untreated
glass slides.
TABLE I
______________________________________
Static Friction and Scratch Resistance of Treated Glass
Treatment
Static Friction Value
Relative
Example Unwashed Water Washed
Scratch Resistance
______________________________________
4 0.101 0.111 1
5 0.320 0.247 3
6 0.173 0.193 2
7 0.096 0.096 1
8 0.103 0.108 1
9 0.257 0.231 3
10 0.183 0.172 2
11 0.091 0.097 1
12 0.105 0.108 1
13 0.318 0.276 3
14 0.098 0.103 1
Untreated
-- 0.348 >>>3
______________________________________
EXAMPLE 16
Water Repellency
The water repellency properties that are imparted to surfaces treated with
emulsions of Examples 5-14 were determined using 2".times.2".times.1.5"
test pieces of concrete that were cut from standard
8".times.16".times.1.5" concrete patio blocks. The blocks were immersed
for 10 minutes in the emulsions of Examples 5-14 which had been diluted to
2.5 wt. % of the starting silane. The excess emulsion was shaken from the
concrete blocks and the blocks were allow to dry in ambient air for 24
hours. The blocks were then immersed in running water for 30 minutes to
remove any residual emulsifier and allowed to dry for 72 hours. The water
repellency of the treated blocks was then determined by placing a drop
(approx. 3/16-inch, 5 mm diameter or 0.05 mL volume) of a test water
solution on the blocks and observing the shape of the drop after 10
seconds. The test water solutions are a series of solutions numbered 1
through 8 containing isopropanol in water at concentrations of 2, 5, 10,
20, 30, 40, 50, and 60 volume percent isopropanol, respectively. The water
repellency rating is the highest numbered test solution for which the
drops remain spherical or hemispherical on the treated surface for at
least ten seconds.
A second determination of water repellency of the same treated concrete
blocks was made by placing a drop of deionized water on the block and
estimating the contact angle of the drop. A contact angle of greater than
100 degrees was rated as Excellent, a contact angle of 80-100 degrees was
rated as Good, an angle of 60-80 as Fair and an angle of less than 60
degrees as Poor.
TABLE II
______________________________________
Water Repellency Of Treated Concrete
Treatment Water Water Repellency
Example Contact Angle
Rating
______________________________________
5 Excellent 3
6 Excellent 3
7 Excellent 4
8 Excellent 3
9 Excellent 4
10 Excellent 4
11 Excellent 4
12 Excellent 3
13 Good 1
Control Poor 0
______________________________________
EXAMPLE 17
Water Repellency of Treated Glass
To exemplify the water repellency that is imparted to glass by the
emulsions of this invention, the water contact angles on treated glass
slides were determined. Two 50.times.70mm precleaned glass slides were
treated with the emulsion of Example 12 which had been diluted to 0.5 wt.
% of the silane. The treatment involved dipping the glass slides into the
emulsion, wiping them dry with a lintless tissue, then rinsing the slides
with flowing deionized water and drying again. This treatment was repeated
a second time on the two slides. One of the two treated slides was then
washed with a standard laboratory glass cleaning detergent, rinsed with
water and dried. The water contact angles were determined on both treated
glass slides by the Sessile Drop method. The treated but unwashed slide
had an advancing water contact angle of 102 degrees and a receding contact
angle of 82 degrees. The slide which was treated and washed with the
detergent had an advancing contact angle of 105 degrees and a receding
contact angle of 82 degrees. These results illustrate the excellent water
repellency of the glass surface that was achieved instantly by simple
contact of the glass substrate with the emulsions of this invention,
without additional curing of the treated substrate. This was due to the
highly reactive nature of the emulsified silane composition. Additionally,
the treatment was durable and could not be removed by washing with
detergents, as one would expect for a silane composition that is
chemically bonded to the substrate.
EXAMPLE 18
Durability of Surface Treatments
The durability of the treatments of glass surfaces with one of the
emulsions of this invention was determined by measuring the change in the
static friction value of a treated glass plate after it was boiled in
water. Glass slides were treated by dipping in the emulsion of Example 12
which was diluted to 0.5%, and wiping until dry with a lintless tissue.
The treated slides were then rinsed with deionized water for 15 seconds
and then dried. The static friction was measured as in Example 15 above.
Then the slides were boiled in deionized water for 30 minutes, dried, and
the static friction values again determined. The slides were then boiled
for an additional 90 minutes and the final static friction values
determined. For comparison, the same sequence was carried out on untreated
glass slides. The results shown in Table III illustrate that the benefits
imparted by the emulsions of this invention are durable even under these
extreme conditions.
TABLE III
______________________________________
Minutes of Boiling
Static Friction Value
Treatment 0 min. 30 min. 120 min.
______________________________________
None 0.580 0.513 0.645
Example 12 0.089 0.128 0.164
______________________________________
EXAMPLE 19
Stability of Emulsions
The emulsions of this invention are stable under ambient conditions for
periods of at least 12 months. The stability under more extreme conditions
is illustrated by this example. Four portions of the emulsion of Example
12 were prepared. The pH of two portions were adjusted from the original
pH value of 2.5 to a value of 7.0 with acetic acid. One portion at pH 2.5
and one at pH 7.0 were stored in an oven at 80.degree. C. for 6 days. No
change in the appearance of the heated emulsions was observed during this
period. After 6 days all four emulsions were diluted to 0.1% and glass
plates were dipped into the emulsions and wiped dry with lintless tissues.
The treated plates were rinsed with water, dried, and the static friction
values determined as in Example 15. The values for the static friction
shown in Table IV illustrate the excellent stability of the emulsions of
this invention.
TABLE IV
______________________________________
Emulsion Stability
Static Friction Value
Emulsion pH
Storage Conditions
of Treated Glass Slides
______________________________________
2.5 Room temperature
0.096
2.5 80.degree. C./6 days
0.106
7.0 Room temperature
0.094
7.0 80.degree. C./6 days
0.107
______________________________________
Having thus described and exemplified the invention with a certain degree
of particularity, it should be appreciated that the following claims are
not to be so limited but are to be afforded a scope commensurate with the
wording of each element of the claim and equivalents thereof.
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